This is a Phase II trial of phenylacetic acid for recurrent malignant glioma being conducted by the North American Brain Tumor consortium (NABTC) and the Southwest Oncology Group (SWOG). It is anticipated that 10 patients will enter this study at the University of Pittsburgh Cancer Institute. Phenylacetate (PAA) will be given at a starting dose of 400 mg/kg/day (Ideal Body Weight) using a continuous intravenous infusion, for 14 days, followed by a 14 day rest. A repeat 14 day infusion will be given, followed by a 14 day rest.